Twist-lock photoelectric controllers (referred to herein as a “photocontrol” or a “photocontroller”) are commonly used to automatically switch luminaires on at dusk and off at dawn. These luminaires are typically used to light roadways, parking lots and other large outdoor areas. These devices sense the intensity of the ambient light and switch the luminaires on and off accordingly. For best performance, the manufacturers of these devices recommend that the user orient the photocontroller so that the cell faces in the direction of North, away from direct sunlight. The manufacturers also require a receptacle that can be easily adjusted to provide the desired orientation.
Street lighting luminaries are typically provided with an electrical receptacle for receiving a photoelectric controller on the luminaire housing. The receptacle, which is mounted on the top of the housing, is electrically wired into the power supply to the luminaire. A photoelectric controller is plugged into the receptacle to provide photoelectric control of the luminaire. The controller has three prongs which are inserted into corresponding openings in the receptacle by applying downward pressure on the controller. After the prongs are completely inserted, the controller is rotated to lock it in place.
After insertion in the receptacle, photoelectric controllers are preferably orientated in a northerly direction (in the northern hemisphere and a southerly direction in the southern hemisphere) to optimize the operation of the photoelectric cell. In one known receptacle, orientation is achieved by loosening a screw in the top of the receptacle, rotating the receptacle until an arrow or other indicia is aimed generally toward North, and then re-tightening the screw. Another receptacle design resiliently attaches the receptacle to the housing surface using a snap ring. By lifting the receptacle, keying pins and recesses in the receptacle and housing are disengaged and the receptacle may be turned to a different orientation.
Within the American National Standards Institute (ANSI), there is a committee, C136, which publishes standards defining some of the mechanical and electrical requirements for different types of lighting equipment, including photocontroller receptacles. The relevant standard relating to the present invention is C136.10-2006, titled “American National Standard for Roadway and Area Lighting Equipment—Locking-type Photocontrol and Mating Devices—Physical and Electrical Interchangeability and Testing.” Photocontroller receptacles sold in the United States are required to comply with this standard.
The twist-lock photocontrollers that are currently used to automatically control luminaires have several disadvantages. Some of the designs require a screw or other fastening device to be loosened before the receptacle can be re-oriented and then the screw has to be re-tightened. Other designs use a spring to secure the receptacle to the luminaire housing but they tend to become loose and water can enter the housing. Therefore, there is a need for a receptacle that can be easily reoriented without using a tool, while still securing the receptacle to the luminaire housing and preventing water from entering.